An automatic vehicle transmission typically includes a shift column having a shift lever that allows a driver to manually switch the transmission between various positions, such as a park, reverse, neutral, drive, and overdrive position, to name but a few. The shift lever contacts a park position detent such that the lever may be selectively held in the park position. In order to avoid a situation where the shift lever is moved from the park to another non-park position, such as the drive position, while an accelerator pedal is depressed which causes the vehicle to inadvertently move forward, various park-lock mechanisms have been developed. Traditionally, park-lock mechanisms included a separate park position switch and brake transmission shift interlock (BTSI), both of which contribute to control movement of the shift lever out of the park position.
Although park-lock mechanisms having separate park position switch and BTSI components have successfully been used throughout the industry, there are certain disadvantages associated with such non-integrated designs. For instance, the non-integrated design reduces the amount of space in the knee bolster area, thereby limiting the stroke of the occupants knees and feet during a collision. Moreover, providing a separate park position switch and BTSI increases the mass, number of parts, assembly time, labor, and cost of the shift column. Also, the combined amount of space required to accommodate the separated components is greater than the amount required to accommodate an integrated component, thus, the non-integrated design reduces the flexibility when designing a shift column.
Furthermore, traditional BTSI designs typically do not provide any separate mechanical override feature. In emergency situations, such as battery failure, a BTSI lacking such a feature would allow the drive to bypass the BTSI and move the shift lever out of the park position detent without depressing the brake pedal and inserting a key into the ignition, as is normally required. Traditionally designed BTSIs are typically located too far forward on the shift column to provide for a mechanical override.
Moreover, current BTSI designs allow the shift lever to move fore and aft while still in the park position detent, thus creating an undesirable amount of play, or stack, in the shift lever. If a driver engages the shift lever in such a system without depressing the brake pedal, even through the shift lever is not removed from the park position detent, there is often times enough play that the park position switch will misinterpret the status of the shift lever. Accordingly, the digital PRNDL or other instrumentation may be sent a signal indicating that the shift lever is no longer in the park position even though it actually is.
It is an object of the present invention to overcome or greatly minimize the foregoing limitations of the prior art.